The pathways of phosphorus metabolism in microorganisms include several enzymatic hydrolyses of chemical bonds to phosphorus which are accelerated enormously relative to the corresponding nonenzymatic reactions. The enzymatic hydrolysis of DNA and structurally similar phosphodiesters is not understood in detail, but the occurrence of a phosphohydrolase in Enterobacter aerogenes which catalyzes the hydrolysis of simple alkyl phosphate mono- and diesters may allow characterization of such an enzyme mechanism. The proposed research will examine the catalytic mechanism of this enzyme through studies of: 1) the dependence of kinetic properties on pH and metal ions, 2) covalent intermediate formation between the enzyme and substrates, 3) the amino acid residues essential for activity, and 4) the effect of asymmetric substrate structure on the hydrolysis product distribution. Alkyl phosphonic acids can serve as sole phosphorus source for E. aerogenes. Alkyl phosphonic acids possessing a Beta-amino group can be degraded to inorganic phosphate with Beta-ketophosphonic acids occurring as stable intermediates. The role of metal ions and amines in catalysis and the existence of metaphosphate anion as a reactive intermediate in dephosphonylation will be investigated in both nonenzymatic and enzymatic reactions. Methyl phosphonic acids must be hydrolyzed through a distinct pathway, which will be elucidated by identification of degradation products obtained from radioactively labelled precursors. The enzyme catalyzing the dephosphonylation reaction will be isolated and its mechanism of action investigated.